diff --git a/moto/redshift/models.py b/moto/redshift/models.py
index 44e944c3b..f0ea9f5f9 100644
--- a/moto/redshift/models.py
+++ b/moto/redshift/models.py
@@ -4,6 +4,7 @@ import copy
 import datetime
 
 import boto.redshift
+from botocore.exceptions import ClientError
 from moto.compat import OrderedDict
 from moto.core import BaseBackend, BaseModel
 from moto.core.utils import iso_8601_datetime_with_milliseconds
@@ -430,6 +431,12 @@ class RedshiftBackend(BaseBackend):
         cluster_identifier = kwargs['cluster_identifier']
         cluster = self.clusters[cluster_identifier]
         if not hasattr(cluster, 'cluster_snapshot_copy_status'):
+            if cluster.encrypted == 'true' and kwargs['snapshot_copy_grant_name'] is None:
+                raise ClientError(
+                    'InvalidParameterValue',
+                    'SnapshotCopyGrantName is required for Snapshot Copy '
+                    'on KMS encrypted clusters.'
+                )
             status = {
                 'DestinationRegion': kwargs['destination_region'],
                 'RetentionPeriod': kwargs['retention_period'],
diff --git a/moto/redshift/responses.py b/moto/redshift/responses.py
index 724a61b68..63945c00b 100644
--- a/moto/redshift/responses.py
+++ b/moto/redshift/responses.py
@@ -506,7 +506,7 @@ class RedshiftResponse(BaseResponse):
         snapshot_copy_kwargs = {
             'cluster_identifier': self._get_param('ClusterIdentifier'),
             'destination_region': self._get_param('DestinationRegion'),
-            'retention_period': self._get_param('RetentionPeriod'),
+            'retention_period': self._get_param('RetentionPeriod', 7),
             'snapshot_copy_grant_name': self._get_param('SnapshotCopyGrantName'),
         }
         cluster = self.redshift_backend.enable_snapshot_copy(**snapshot_copy_kwargs)
diff --git a/tests/test_redshift/test_redshift.py b/tests/test_redshift/test_redshift.py
index 79da9f193..32deb74bc 100644
--- a/tests/test_redshift/test_redshift.py
+++ b/tests/test_redshift/test_redshift.py
@@ -1047,12 +1047,13 @@ def test_tagged_resource_not_found_error():
 def test_enable_snapshot_copy():
     client = boto3.client('redshift', region_name='us-east-1')
     client.create_cluster(
-        DBName='test',
         ClusterIdentifier='test',
         ClusterType='single-node',
-        NodeType='ds2.xlarge',
+        DBName='test',
+        Encrypted=True,
         MasterUsername='user',
         MasterUserPassword='password',
+        NodeType='ds2.xlarge',
     )
     client.enable_snapshot_copy(
         ClusterIdentifier='test',
@@ -1067,6 +1068,27 @@ def test_enable_snapshot_copy():
     cluster_snapshot_copy_status['SnapshotCopyGrantName'].should.equal('copy-us-east-1-to-us-west-2')
 
 
+@mock_redshift
+def test_enable_snapshot_copy_unencrypted():
+    client = boto3.client('redshift', region_name='us-east-1')
+    client.create_cluster(
+        ClusterIdentifier='test',
+        ClusterType='single-node',
+        DBName='test',
+        MasterUsername='user',
+        MasterUserPassword='password',
+        NodeType='ds2.xlarge',
+    )
+    client.enable_snapshot_copy(
+        ClusterIdentifier='test',
+        DestinationRegion='us-west-2',
+    )
+    response = client.describe_clusters(ClusterIdentifier='test')
+    cluster_snapshot_copy_status = response['Clusters'][0]['ClusterSnapshotCopyStatus']
+    cluster_snapshot_copy_status['RetentionPeriod'].should.equal(7)
+    cluster_snapshot_copy_status['DestinationRegion'].should.equal('us-west-2')
+
+
 @mock_redshift
 def test_disable_snapshot_copy():
     client = boto3.client('redshift', region_name='us-east-1')